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1.1 etheisen 1: /*
1.9 ! shadchin 2: * Copyright (C) 1984-2012 Mark Nudelman
1.1 etheisen 3: *
1.5 millert 4: * You may distribute under the terms of either the GNU General Public
5: * License or the Less License, as specified in the README file.
1.1 etheisen 6: *
1.9 ! shadchin 7: * For more information, see the README file.
1.1 etheisen 8: */
9:
10:
11: /*
12: * Primitives for displaying the file on the screen,
13: * scrolling either forward or backward.
14: */
15:
16: #include "less.h"
17: #include "position.h"
18:
19: public int screen_trashed;
20: public int squished;
1.5 millert 21: public int no_back_scroll = 0;
1.7 shadchin 22: public int forw_prompt;
1.1 etheisen 23:
1.8 millert 24: extern volatile sig_atomic_t sigs;
1.1 etheisen 25: extern int top_scroll;
26: extern int quiet;
27: extern int sc_width, sc_height;
28: extern int plusoption;
29: extern int forw_scroll;
30: extern int back_scroll;
31: extern int ignore_eoi;
1.5 millert 32: extern int clear_bg;
33: extern int final_attr;
1.7 shadchin 34: extern int oldbot;
1.1 etheisen 35: #if TAGS
36: extern char *tagoption;
37: #endif
38:
39: /*
40: * Sound the bell to indicate user is trying to move past end of file.
41: */
42: static void
43: eof_bell()
44: {
45: if (quiet == NOT_QUIET)
46: bell();
47: else
48: vbell();
49: }
50:
51: /*
1.7 shadchin 52: * Check to see if the end of file is currently displayed.
1.1 etheisen 53: */
1.7 shadchin 54: public int
55: eof_displayed()
1.1 etheisen 56: {
57: POSITION pos;
58:
59: if (ignore_eoi)
1.7 shadchin 60: return (0);
61:
62: if (ch_length() == NULL_POSITION)
63: /*
64: * If the file length is not known,
65: * we can't possibly be displaying EOF.
66: */
67: return (0);
68:
1.1 etheisen 69: /*
70: * If the bottom line is empty, we are at EOF.
71: * If the bottom line ends at the file length,
72: * we must be just at EOF.
73: */
74: pos = position(BOTTOM_PLUS_ONE);
1.7 shadchin 75: return (pos == NULL_POSITION || pos == ch_length());
76: }
77:
78: /*
79: * Check to see if the entire file is currently displayed.
80: */
81: public int
82: entire_file_displayed()
83: {
84: POSITION pos;
85:
86: /* Make sure last line of file is displayed. */
87: if (!eof_displayed())
88: return (0);
89:
90: /* Make sure first line of file is displayed. */
91: pos = position(0);
92: return (pos == NULL_POSITION || pos == 0);
1.1 etheisen 93: }
94:
95: /*
96: * If the screen is "squished", repaint it.
97: * "Squished" means the first displayed line is not at the top
98: * of the screen; this can happen when we display a short file
99: * for the first time.
100: */
1.7 shadchin 101: public void
1.1 etheisen 102: squish_check()
103: {
104: if (!squished)
105: return;
106: squished = 0;
107: repaint();
108: }
109:
110: /*
111: * Display n lines, scrolling forward,
112: * starting at position pos in the input file.
113: * "force" means display the n lines even if we hit end of file.
114: * "only_last" means display only the last screenful if n > screen size.
115: * "nblank" is the number of blank lines to draw before the first
116: * real line. If nblank > 0, the pos must be NULL_POSITION.
117: * The first real line after the blanks will start at ch_zero().
118: */
119: public void
120: forw(n, pos, force, only_last, nblank)
1.5 millert 121: register int n;
1.1 etheisen 122: POSITION pos;
123: int force;
124: int only_last;
125: int nblank;
126: {
127: int eof = 0;
128: int nlines = 0;
129: int do_repaint;
130: static int first_time = 1;
131:
132: squish_check();
133:
134: /*
135: * do_repaint tells us not to display anything till the end,
136: * then just repaint the entire screen.
137: * We repaint if we are supposed to display only the last
138: * screenful and the request is for more than a screenful.
139: * Also if the request exceeds the forward scroll limit
140: * (but not if the request is for exactly a screenful, since
141: * repainting itself involves scrolling forward a screenful).
142: */
143: do_repaint = (only_last && n > sc_height-1) ||
144: (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
145:
146: if (!do_repaint)
147: {
148: if (top_scroll && n >= sc_height - 1 && pos != ch_length())
149: {
150: /*
151: * Start a new screen.
152: * {{ This is not really desirable if we happen
153: * to hit eof in the middle of this screen,
154: * but we don't yet know if that will happen. }}
155: */
1.5 millert 156: pos_clear();
157: add_forw_pos(pos);
158: force = 1;
1.7 shadchin 159: clear();
1.1 etheisen 160: home();
161: }
162:
163: if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
164: {
165: /*
166: * This is not contiguous with what is
167: * currently displayed. Clear the screen image
168: * (position table) and start a new screen.
169: */
170: pos_clear();
171: add_forw_pos(pos);
172: force = 1;
173: if (top_scroll)
174: {
1.7 shadchin 175: clear();
1.1 etheisen 176: home();
177: } else if (!first_time)
178: {
179: putstr("...skipping...\n");
180: }
181: }
182: }
183:
184: while (--n >= 0)
185: {
186: /*
187: * Read the next line of input.
188: */
189: if (nblank > 0)
190: {
191: /*
192: * Still drawing blanks; don't get a line
193: * from the file yet.
194: * If this is the last blank line, get ready to
195: * read a line starting at ch_zero() next time.
196: */
197: if (--nblank == 0)
198: pos = ch_zero();
199: } else
200: {
201: /*
202: * Get the next line from the file.
203: */
204: pos = forw_line(pos);
205: if (pos == NULL_POSITION)
206: {
207: /*
208: * End of file: stop here unless the top line
209: * is still empty, or "force" is true.
1.5 millert 210: * Even if force is true, stop when the last
211: * line in the file reaches the top of screen.
1.1 etheisen 212: */
213: eof = 1;
214: if (!force && position(TOP) != NULL_POSITION)
215: break;
1.5 millert 216: if (!empty_lines(0, 0) &&
217: !empty_lines(1, 1) &&
218: empty_lines(2, sc_height-1))
219: break;
1.1 etheisen 220: }
221: }
222: /*
223: * Add the position of the next line to the position table.
224: * Display the current line on the screen.
225: */
226: add_forw_pos(pos);
227: nlines++;
228: if (do_repaint)
229: continue;
230: /*
231: * If this is the first screen displayed and
232: * we hit an early EOF (i.e. before the requested
233: * number of lines), we "squish" the display down
234: * at the bottom of the screen.
235: * But don't do this if a + option or a -t option
236: * was given. These options can cause us to
237: * start the display after the beginning of the file,
238: * and it is not appropriate to squish in that case.
239: */
240: if (first_time && pos == NULL_POSITION && !top_scroll &&
241: #if TAGS
242: tagoption == NULL &&
243: #endif
244: !plusoption)
245: {
246: squished = 1;
247: continue;
248: }
249: put_line();
1.7 shadchin 250: #if 0
251: /* {{
252: * Can't call clear_eol here. The cursor might be at end of line
253: * on an ignaw terminal, so clear_eol would clear the last char
254: * of the current line instead of all of the next line.
255: * If we really need to do this on clear_bg terminals, we need
256: * to find a better way.
257: * }}
258: */
259: if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
1.5 millert 260: {
261: /*
262: * Writing the last character on the last line
263: * of the display may have scrolled the screen.
264: * If we were in standout mode, clear_bg terminals
265: * will fill the new line with the standout color.
266: * Now we're in normal mode again, so clear the line.
267: */
268: clear_eol();
269: }
1.7 shadchin 270: #endif
271: forw_prompt = 1;
1.1 etheisen 272: }
273:
274: if (nlines == 0)
275: eof_bell();
276: else if (do_repaint)
277: repaint();
278: first_time = 0;
279: (void) currline(BOTTOM);
280: }
281:
282: /*
283: * Display n lines, scrolling backward.
284: */
285: public void
286: back(n, pos, force, only_last)
1.5 millert 287: register int n;
1.1 etheisen 288: POSITION pos;
289: int force;
290: int only_last;
291: {
292: int nlines = 0;
293: int do_repaint;
294:
295: squish_check();
296: do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
297: while (--n >= 0)
298: {
299: /*
300: * Get the previous line of input.
301: */
302: pos = back_line(pos);
303: if (pos == NULL_POSITION)
304: {
305: /*
306: * Beginning of file: stop here unless "force" is true.
307: */
308: if (!force)
309: break;
310: }
311: /*
312: * Add the position of the previous line to the position table.
313: * Display the line on the screen.
314: */
315: add_back_pos(pos);
316: nlines++;
317: if (!do_repaint)
318: {
319: home();
320: add_line();
321: put_line();
322: }
323: }
324:
325: if (nlines == 0)
326: eof_bell();
327: else if (do_repaint)
328: repaint();
1.7 shadchin 329: else if (!oldbot)
330: lower_left();
1.1 etheisen 331: (void) currline(BOTTOM);
332: }
333:
334: /*
335: * Display n more lines, forward.
336: * Start just after the line currently displayed at the bottom of the screen.
337: */
338: public void
339: forward(n, force, only_last)
340: int n;
341: int force;
342: int only_last;
343: {
344: POSITION pos;
345:
1.7 shadchin 346: if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
1.1 etheisen 347: {
348: /*
349: * If the -e flag is set and we're trying to go
350: * forward from end-of-file, go on to the next file.
351: */
352: if (edit_next(1))
353: quit(QUIT_OK);
354: return;
355: }
356:
357: pos = position(BOTTOM_PLUS_ONE);
358: if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
359: {
360: if (ignore_eoi)
361: {
362: /*
363: * ignore_eoi is to support A_F_FOREVER.
364: * Back up until there is a line at the bottom
365: * of the screen.
366: */
367: if (empty_screen())
368: pos = ch_zero();
369: else
370: {
371: do
372: {
373: back(1, position(TOP), 1, 0);
374: pos = position(BOTTOM_PLUS_ONE);
375: } while (pos == NULL_POSITION);
376: }
1.5 millert 377: } else
378: {
1.1 etheisen 379: eof_bell();
380: return;
381: }
382: }
383: forw(n, pos, force, only_last, 0);
384: }
385:
386: /*
387: * Display n more lines, backward.
388: * Start just before the line currently displayed at the top of the screen.
389: */
390: public void
391: backward(n, force, only_last)
392: int n;
393: int force;
394: int only_last;
395: {
396: POSITION pos;
397:
398: pos = position(TOP);
399: if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
400: {
401: eof_bell();
402: return;
403: }
404: back(n, pos, force, only_last);
405: }
406:
407: /*
408: * Get the backwards scroll limit.
409: * Must call this function instead of just using the value of
410: * back_scroll, because the default case depends on sc_height and
411: * top_scroll, as well as back_scroll.
412: */
413: public int
414: get_back_scroll()
415: {
1.5 millert 416: if (no_back_scroll)
417: return (0);
1.1 etheisen 418: if (back_scroll >= 0)
419: return (back_scroll);
420: if (top_scroll)
421: return (sc_height - 2);
422: return (10000); /* infinity */
423: }